I'm not sure how accurate this method is but it seems I'm on the narrow side (around 100mm). So basically I'm looking for a narrow saddle suitable for a skinny arsed freak. My most comfortable and narrow saddle is the Fizik Gobi but I still get pain on my sit bones. Can anyone recommend anything please?

You obviously don't have narrow sit bones or a basic grasp of anatomy.

So why are the pads in bib shorts all the same width?

Yes, there are variations in the width of ischial tuberosities, but given that cyclists have managed for 70 odd years without measuring sitbone distance, is it likely that we have stumbled upon a major problem, or is it more likely that we have stumbled upon something that can be used to set our saddle selling procedure apart from our competitors?

My grasp of basic anatomy is probably a good deal better than yours; I've been looking at it for 25 years.

Then you can appreciate that people with narrow sit bones and the narrower 'gap in the middle' that sometimes comes with them get friction from the edges of wider saddles at the top of the thights, especially if they ride a road bike with a narrower Q-factor. People come in different shapes and sizes, that is why some saddles are narrower than others.
Never had my sit bones measured but I did have a brooks B17 saddle given to me after a friend had broken it in over a few 1000miles, his sit bones were clearly marked in the leather and after some use mine were visible 2cm narrower and further back, I swapped it for a brooks swift that was narrower and more comfortable.

As for padded shorts? No idea if they are size specific, they certainly are more flexible and conform to the body more than a saddle.

Specialized toupe, San Marco Regale and the narrower pro-logos work for me.

I don't understand how offering a saddle in a range of sizes is a marketing ploy seeing as you'd buy the one in the 'right' size and have a saddle. If they didn't offer a range of sizes you'd buy a saddle. Either way you've bought a saddle, are they more expensive in different sizes?

Crikey - I have 2 specialized toupe saddles one in 130 and the other 143, I can sit on the 130 for any length of time and have done 100 mile sportives on it, yet the 143 has my ariss numb and painful and me crying in 15 min or so, could you explain why this is?

Charge Knife has a pretty narrow hull- I've got the body dimensions of a scaffold pipe and most saddles just feel daft to me, it's not so much pressure points (I have a cast iron arse) as just being in the bloody way- it's the same effect as a wider person using a saddle that's about half again as wide as it needs to be.

Course, the Knife also has almost no padding so fit's really critical, try before you buy if you can.

can having a saddle which is too wide cause numb peenor as well or just arse ache?

Struggling to find one which works for my road bike, no speci dealers nearby to take the test. Getting achey arse as well as numb gentlemans vegetables tried different angles etc, and various saddles (bel air, spoon, etc) thinking maybe a knife might be worth a shot.

If you don't like the Gobi, try a WTB? Feels like the opposite kind of shape to me. I can't sit on a Gobi for 5mins. The Volt and Rocket V are under 127mm wide and the most comfy saddles I've used. Pure V and Laser Vs are also good but a bit wider. I have a Pure V FS if you're interested, as I use Rocket/Volts on all my bikes now. No idea of how my sit bones measure up but the saddles are comfy for me.

So just been for a spin on new saddle and arse as sore as ever! Dropping to a narrower saddle ain't made much difference other than better pedalling efficiency..
Will tweak about with position before returning!